The invention relates to a method for the electrical and mechanical surface passivation of sensors, e.g., semiconductor sensors, using a vacuum apparatus having a tank provided with connections for gas inlet and outlet lines, an anode and a cathode over which a substrate holding device is mounted for the purpose of coating the sensor with a layer of material by the CVD process, with plasma enhanced deposition, and provided with an apparatus for the measurement and control of the parameters governing the sputtering process, such as gas flow, pressure, and the electrical power input into the plasma. During the manufacture of electronic components such as sensors, for example, especially semiconductor sensors, microchip components and other highly integrated components to name but a few, it is necessary to protect the outer surface of the body of the component both against external influences and internal short-circuits. Because of the highly detailed, fine grain structure of micromechanical semiconductor sensors, as in the case of pressure sensors, the application of conductors on the sensor surfaces calls for electrically insulating intermediate layers for the prevention of electrical short-circuits to the basic substrate of the sensor. Also in the case of telemetering components exposed to a chemically aggressive atmosphere it is necessary to provide a protective coating to the component so as to improve its stability and resistance to a corrosive environment.
Existing classical coating methods, such as thermal vapor deposition or the sputtering of certain substances, has been used for the purpose of applying such protective and insulating coatings to the base substrate. Disadvantages are high working temperatures which make it impossible to coat heat-sensitive substrate, and the fact that the coating parameters, such as hardness, density, electrical properties, refractive index and the composition of the coating, can be controlled only to a limited extent.
For the low-cost production of coatings on such substrate in large numbers, there is also a need for a simple process under stable conditions to achieve the desired results.
The invention is addressed to the problem of devising a method for the electrical and mechanical surface passivation of sensors, such as semiconductor sensors, using a vacuum apparatus, such that the protective coatings that can be produced by the method of the invention can be created with high stability and repeatability, as well as with high rates of deposition, on a large industrial scale. Furthermore, the coatings are to have a controllable high density, low surface roughness, high strengths of adhesion and great resistance to corrosion. Furthermore, the working materials involved in the coating process are to be inexpensive and have environmentally acceptable properties.